Thread: Stainless blades

Originally Posted by Gammaray

Excuse me for sweating the details, but it is the HARDNESS of stainless that makes it both more scratch resistant and more difficult to hone.

If you like details. Vintage Friodurs are made of 440 C which is not functionally harder than most carbon steel.
If you're talking about newer exotic SS then it may be on par with carbon for a high Rockwell level but not harder.

Originally Posted by Gammaray

The metallurgists on this forum may take issue with characterizing stainless or carbon as "harder" or "tougher" than another. The formulations and characteristics of stainless or carbon steel are complex and dependent upon many alloying factors not the least of which is the tempering process.

I know less about the exact composition of my SR steel than I do my hunting and pocket knives, but there are some key physical characteristics needed to make a good razor. That main two are HARDNESS and TOUGHNESS. Hardness, like the Rockwell standard, is a measure of compression taken with a very hard probe. Most knives and razors come in at 57-62 Rockwell. Most of our razors come in at this level. This is actually one of the easier parameters to achieve by way of heat treating, and it is hardness that determines potential sharpness. But too much can make it too brittle resulting in a very fine edge that breaks off like glass while shaving. Toughness, is a measure of flexibility (to bend and return to its original form). This is a very important parameter for retaining a fine edge while shaving. This is accomplished by tempering. The process comes after the HIGH heat hardening step by reheating to a lower temperature ~400-1200 F depending on the alloy, followed by a quenching quick cool in water, oil, dry ice (stainless), or even wet mud (Japanese). Dovo and Thiers Issard quench carbon blades in a 1200 F degree bath of liquid lead.

Both carbon and stainless can exhibit excellent hardness and toughness. But in general, stainless is more likely to snap when bent due to the chrome alloy, although today's stainless alloys are much more resistant to breaking than in the past. Carbon can generally be made much tougher than stainless and is the preferred alloy for tool steel. Laminated or Damascus carbon steel knives are incredibly tough able to be bent to 90 degrees without breaking.

If made properly, both stainless and carbon steel can exhibit ideal properties for a SR with stainless having the additional advantage of rust resistances.

Thank you for really making an effort. Learned a lot!

Originally Posted by Gammaray

Excuse me for sweating the details, but it is the HARDNESS of stainless that makes it both more scratch resistant and more difficult to hone.

TOUGHNESS is related to flexibility (ability to return to its original state after being bent or torqued).

It's not the hardness of the steel, it's the hardness of the carbides in the steel. The stainless razors themselves will not be any harder on a rockwell hardness tester than a carbon steel razor, and it's likely that they will be softer than vintage carbon steel razors that were intended for barbers and made with a hard temper.

Chromium carbides, Vanadium carbides, Tungsten carbides....all are extremely hard. But the steel overall is not, the carbides in it are. They are what give the wear resistance, not the hardness of the overall alloy.

Originally Posted by DaveW

It's not the hardness of the steel, it's the hardness of the carbides in the steel. The stainless razors themselves will not be any harder on a rockwell hardness tester than a carbon steel razor, and it's likely that they will be softer than vintage carbon steel razors that were intended for barbers and made with a hard temper.

Chromium carbides, Vanadium carbides, Tungsten carbides....all are extremely hard. But the steel overall is not, the carbides in it are. They are what give the wear resistance, not the hardness of the overall alloy.

Agreed, but you cannot separate the carbides from the alloy. The fact is carbon steel can easily be hardened to unbelievable Rockwell levels that are of course too brittle to be useful. SO CAN STAINLESS steel. The main advantage with stainless steel is its resistance to rust. Ceteris Paribis (all things being equal) if rust resistance is not necessary then a properly hardened and tempered carbon steel will outperform stainless in terms of toughness. The hardness can be very close but carbon is tougher - period. Where are those rust resistant shock absorbers on trains and cars - that's right they are all carbon steel for a reason. The rust resistance would certainly be appreciated in these applications but stainless steel (even the best alloys) could never be tough enough to spring back and forth a million times without fatigue. Carbon steel is still the king of toughness. Here is an example where stainless steel could never pass the toughness test.

I know you will enjoy this video of a Master Bladesmith Test. Only one type of blade will pass – san mai (Japanese) or Damascus (American) laminated carbon steel blades. Stainless steel need not apply.

1. Cut a 1” hemp rope in one swing.
2. Chop through a 2x4 twice.
3. Shave arm hair after these two tests.
4. Pass blade examination by a Master Bladesmith.
5. Bend the blade in a vice to 90 degrees without metal fracture.

I struggled with my Boker stainless blade when I first received it. After several tries it just did not do as well as its brother The King Cutter. I communicated with SRD and told them my problem. They suggested I send it back which I did. After receiving it back, I used it on about a five days' growth. Shaved like a charm. Used again this AM, the same thing. No harsh feeling on the face. Only smoothness. This was my first stainless after shaving with regular carbon blades for years. I shall buy at least another one.

Originally Posted by Gammaray

Agreed, but you cannot separate the carbides from the alloy.

Somewhere you're getting mixed up with hardness and separability of carbides from a diemaking or toolmaker's steel.

The rockwell test does just that, it tests the hardness of the entire alloy, and not just the hardest part of it.

Back to the original claim, that stainless razors are harder than carbon steel razors - it is not true. Stainless has carbides in it, depending on the alloy, probably different carbides for corrosion resistance. So does high speed steel, for a different reason (to increase the tempering temperature).

In terms of toughness (without regard to knife tests, etc), all you have to do is go to latrobe steel's page and look at their toughness charts for powder and non powder diemaking and high speed steels versus carbon steels. The carbon steels are not the toughest of the bunch. It's not that simple, and you really have to get down to the measured method. D2 is tougher than carbon steel in general, but at 18 degrees, it will not be. Same with A2.

But don't get away from the fundamental issue here, in the steels that are used for razors, a chromium, vanadium or tungsten carbide doesn't make the alloy harder than another alloy that doesn't have them.

Holy crap batman,

There are some freaking smart people on this forum.......... But Iwant to set you all straight, (pun intended), I am not one of them! But ya all are giving me a history lesson here. We are in some way covering history, right? Don't worry, I suck at history too, unless I am making it.

That's right cupcakes, I pulled the trigger on a Dovo bismark, and the masters. And now my wife says I am history, joke.....Carbon, and a stainless. And now that I be a edumacated jarhead, my chin and other areas, (my hemorrhoids are disappearing) will be much more thankful. But the wife is putting size 7 foot down, (thank GOD she is not putting it up }#%€¥£&:;@-) and says no more pricey razors until I stop dragging my knuckles and shave them!

I am out of here, popping smoke

Charlie in Reno

Just about everyone has a few bits of the truth on either side of the argument. The traditional balance of hardness against toughness, speaking of steels, used to preclude having both at the same time. Some myths persist and some are known not to be. But, phases in carbon steels that put this myth to rest are not so easy in the high alloy steels and they remain subject to a delicate balance between hardness and toughness.

Hardness is the same whether the alloy is carbon or stainless. It is a relative measure of the pressure a diamond indenter needs to push into a sample. R(a,b,c) of X value (or Vickers or Mohs) is the same in both types of steel. What was not yet mentioned is microhardness testing that will determine the hardness of even a single carbide. But most generally the space between carbides must also be included in the hardness testing since the majority of us who own testing machines do not have microhardness testers. For that matter, I'm practical, I want to know that the general material is hard or not, not the individual carbides. An individual carbide does not illuminate the properties of the combined strength, or weaknesses, of all the material. when I'm heat treating, I'm heating the whole blade not individual components.

Chromium really likes to make big carbides especially when it's overheated for too long. A bigger carbide has more fracture planes in a relatively larger carbide surface area. Vanadium is added to make smaller carbides, that have a larger surface area to bear the strain than a larger crystal. So, chromium alloys are not as tough as vanadium alloys. But there has been a lot of progress in the world of crucible particle metallurgy and some of the CPM versions of ATS34 and 154CPM are a huge improvement over the previous cast alloys. The new alloys the S-series (S30V et al) are all capable of excellent, world class, sharpness and abrasion resistance and are rust resistant. Those smaller tight carbides are a real difference when compared to looking at the old SS alloys.

The high alloy steels are subject to greater risk in achieving the balance between hardness and toughness than carbon steels. For that reason, less hardness is acceptable to achieve greater toughness. Less hardness can be interpreted as easier to sharpen, or less edge retaining when shaving because abrasion resistance is a combination of both.

None of us, in their right mind, would subject a razor to the ABS kind of stress testing. Don't get me wrong, it's fun to watch, it's fun to do. It shows one type of heat treatment and not necessarily, would that maker sell a knife with that kind of heat treatment. It's only to pass that test.

No one on this site who hones razors would ever agree that shaving arm hair is sufficient to show that it will shave a face in the manner it is expected. It indicates the right direction but it's not enough all by itself to demonstrate shave readiness.

Given the same hardness and the same bevel angle, I suspect that shaving with either carbon or stainless will remain a highly subjective experience. The same might be said for a ceramic blade but those crystals could be considered harder than those in steels. Will it shave better? It will likely shave longer and be harder to hone.

If we stick to a blade that is metallic, and hard and tough and abrasion resistant, buy some stellite or talonite or the like. Those would be an incredibly mean joke to play on your favorite honer. I've had some complaints about a few of my blades (carbon) that were too hard. I regard that feedback as desirable because it shows that the sweet spot for performance is somewhere below the possible potential of the material.

My disclaimer in all this is that I am very fond of carbon steels. There are many fewer forging steels (there are some though) in the stainless materials. Even the classic traditional steels can perform surprisingly well and are often under-rated because of the rush after the modern-latest-greatests. Over the years I've seen good and bad examples of both kinds.

A few of us just had this sort of discussion over a sushi table last weekend. There were thousands, perhaps millions, of great shaving old razors made during a day when none of this stuff was known. A great many of you have, hone and shave with exactly those sorts of blades. Often in preference to new stuff. If it was good enough for guys who had no idea that the stuff we now know about metallurgy was around the corner, and still made some damn fine razors. Why is it a problem now?

In the end, if it gets hair off and you like it...its good. Let the hype sleep.

Well Said, Mike.
Appreciate the voice of reason.
Adam

Carbon and Stainless steel alloys today are superior to anything in the past and may be considered MORE than adequate for shaving.

I have nothing further to say on the matter.

Good day,

Gammaray